Numerous types of materials, such as timber, lumber, bricks, pallets, pipe, I-beams and other structural components, as well as manufactured goods of many types, are transported in bulk by road or rail. A frequent loading configuration is to stack a quantity of material on a flat bed or platform and attempt to restrain the load using one or more cables, chains or straps attached to the sides of the platform. Typically, ratchet winches are provided which permit the restraining means to be placed in tension over the load and prevent the release or counter rotation of the winch. In transit, however, the load may shift or settle, causing the tension in the load restraining means to be reduced, i.e., to slacken, permitting further shifting of the load. This is a highly undesirable and unsafe condition.
Others have attempted to provide devices which maintain a cable, chain, strap or other means for restraining a load in tension against a shifting load. For example, U.S. Pat. No. 2,991,975 discloses a load binder for retaining cables under tension. The device disclosed provides a primary ratchet which is used to initially tighten a cable. Subsequent tightening is accomplished using a set of gears, which multiply the torque applied to permit a greater tension than would be obtained by the primary ratchet alone. Disposed coaxially between a shaft and the cable spool is a coil spring. As the primary ratchet is initially manipulated, the spring begins to be "wound." When the spring has reached the limit of available rotation, the torque is then transferred to the cable spool and initial tension is placed on the cable. If the load shifts, the built up tension in the spring urges against the cable spool and maintains tension proportional to the spring force. A disadvantage of this design is the requirement that a maximum torque be applied to the spring each time the device is used.
U.S. Patent Re. 30,307 discloses a cable take up load binder directed to maintaining a cable or chain in tension against a possibly shifting load. The device utilizes a torque spring positioned between the take up spool and a secondary ratchet means, which is in addition to a primary ratchet means which applies and locks the winch spool in place. The second ratchet is used to apply a load to the torque spring, which is wound coaxial with the winch spool. The winch spool may rotate independently of the primary ratchet, however. Thus if the chain or cable loosens, the force provided by the torque spring rotates the winch spool, but not the primary ratchet.
A problem with both these designs is that the amount of torque applied and the rotation the winch spool can undergo to take up slack are limited by the design of the torque spring. Under certain conditions, after the spring has already "unwound" the spring force may not sufficiently tension the cable or chain and, since the primary ratchet which restrains the cable spool has not been advanced, the restraining means may slip back--limited only by the initial setting of the primary ratchet.
A further recurring problem with the cable tension winches described above is that most designs leave the cable, chain or strap exposed to theft. It is impractical to lock each cable end to the winch body after the load is removed. Since the winches are part of transportation equipment which is used in numerous locations which are often many miles apart and by numerous individuals who may be employed by a number of different entities, it would be impractical to maintain individually keyed locks. If the locks were sufficiently standardized, it would become commensurately less difficult for thieves to obtain keys. Locks also add an unnecessary time consuming operation to the loading and unloading process. Even in those designs providing winch covers, therefore, locks remain impractical. It would therefore be desirable to provide a locking mechanism which would deter casual theft, but which would be conveniently operable by those closely related to the transportation system.